As is well known, strict quality requirements against surface shape displacement (warpage) are actually imposed on glass sheets to be used for flat panel displays (hereinafter referred to as “FPDs”), such as a liquid crystal display, a plasma display, a field emission display (including a surface emission display), an electroluminescent display, and an OLED display, and sheet-like members typified by tempered glass to be used for touch panels.
Hitherto, the warpage of the sheet-like member of this type has been generally measured under a state in which the sheet-like member is set stationary. Various methods for measurement in such a stationary state have been proposed or put into practical use.
Specifically, in Patent Literature 1, there is disclosed a configuration in which a member to be measured such as a glass substrate for an FPD is placed and held on a measurement stage (measurement base stone surface plate), and a plurality of air scanners for measuring surface shape displacement of the member to be measured in a non-contact manner are provided at predetermined intervals. The configuration includes a drive mechanism for moving the air scanners in directions of the X and Y axes.
Further, in Patent Literature 2, there is disclosed a configuration including holding means for holding, for a predetermined period of time, a sheet-like member stopped at a predetermined position of a roller conveyor for conveying the sheet-like member, a frame arranged below the sheet-like member at the predetermined position and is capable of ascending and descending, and height measurement means such as dial gauges, which are arranged on the frame to measure height positions of the sheet-like member at a plurality of points.